Brittle Fracture Avoidance Technology in Large Structures with Thick Steel Plates

2021 ◽  
Vol 21 (9) ◽  
pp. 4926-4930
Author(s):  
Gyubaek An ◽  
Jeongung Park ◽  
Hongyeol Bae
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Brittle Fracture ◽  
Steel Plate ◽  
Control Process ◽  
Brittle Crack ◽  
Fine Grain ◽  
Nano Structures ◽  
Class Steel ◽  
Thick Steel

The 460-MPa-class steel was developed by thermomechanical control process for shipbuilding, and the maximum plate thickness was 100 mm, which has the fine grain size as 5–20 µm. The surfaces were studied in terms of micro and nano structures, surface roughness, and surface energy to evaluate the effect of fracture toughness in large steel structure. The thick steel plate has possibility to occur unstable fracture because the fracture toughness will be decrease with increase of thickness. The increase in the temperature in thermomechanical control process accelerated the surface energy and created both micro and nano structures on the surfaces more effectively. It was effective to avoid brittle fracture in the base metal when the brittle crack was deviated into base metal. The developed 460-MPa-class steel plate improves the brittle fracture safety despite being a thick steel plate through the fine grain size. They had to be designed in such a manner as to avoid crack initiation, especially in welded joints. In this study, brittle crack arrest designs were developed for large weld construction using arrest design concept and micro and nano structures in high strength steel plate.

Effect of Microcast-X Fine Grain Casting on the Microstructure and Mechanical Properties of K492M Alloy at 760°C

2016 ◽  
Vol 849 ◽  
pp. 549-556
Author(s):  
Pin Pin Hu ◽  
Qi Dong Gai ◽  
Qing Li ◽  
Xin Tang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Rupture Life ◽  
Stress Rupture ◽  
Casting Alloy ◽  
Stress Rupture Life ◽  
Casting Technique ◽  
Conventional Casting ◽  
Fine Grain

The effect of Microcast-X fine grain casting on the microstructure and mechnical property K492M alloy at 760°C of was investigated. The results indicated that Microcast-X fine grain casting decreased grain size and dendrite space of γ′ phase and γ/γ′ eutectic. In addition, the element segregation decreased significantly compared to conventional casting technique. Also, the size and distribution of MC carbide were improved. By Microcast-X fine grain casting, the tensile strength increased from 934MPa of conventional casting alloy to 1089MPa and the elongation increased from 1.9% to 5.7%. In addition, the stress-rupture life increased from 28.8h of conventional casting alloy to 72.5h. And the fracture mechanism for the alloys by Microcast-X fine grain casting is trans-granular fracture toughness.

Fracture Toughness of Thick Steel Plates for Shipbuilding

2008 ◽  
Vol 580-582 ◽  
pp. 89-92
Author(s):  
Joon Sik Park ◽  
B.Y. Jung ◽  
Hiroshi Yajima ◽  
Jong Bong Lee
Keyword(s):  
Fracture Toughness ◽  
Crack Initiation ◽  
Large Scale ◽  
Steel Plate ◽  
Plate Thickness ◽  
Steel Plates ◽  
Initiation And Propagation ◽  
Thick Steel ◽  
Test Result ◽  
Grade Steel

In this study, the effect of thickness on the fracture toughness of the steel plate with the thickness of 80mm has been investigated by the wide plate tensile test and ESSO test. The fracture toughness for crack initiation and propagation was evaluated quantitatively for the full thickness specimen. It was found that EH-36 grade steel with the thickness of 80mmt showed the KIC value of 164kgf/mm1.5 at -145°C. Also, large-scale ESSO test result showed that the steel with the thickness of 80mm had 520kgf/mm1.5 at -10°C. Although it was known that the fracture toughness decreases with the increase of the plate thickness, EH-36 grade steel with the thickness of 80mm had enough values of fracture toughness to prevent the crack initiation and arrest the brittle crack propagation.

scholarly journals Fracture Toughness of Thick Steel Plate for Ship Building

2007 ◽  
Vol 25 (4) ◽  
pp. 15-19 ◽  
Author(s):  
Jeong-Ung Park ◽  
Gyu-Baek An
Keyword(s):  
Fracture Toughness ◽  
Steel Plate ◽  
Ship Building ◽  
Thick Steel

Consideration on the Toughness Requirement to the Austenitic Weld Metal in the LNG Storage Tanks Subjected to a Partial Height Hydro Test

2010 ◽  
Vol 638-642 ◽  
pp. 3679-3686 ◽  
Author(s):  
Tomoya Kawabata ◽  
Noboru Konda ◽  
Kazushige Arimochi ◽  
Hitoshi Hirose ◽  
Seiichi Muramoto ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Steel Plate ◽  
Strength Distribution ◽  
Storage Tanks ◽  
Brittle Crack ◽  
British Standard Institute ◽  
High Level ◽  
Heterogeneous Base ◽  
Full Height

PD7777 published by British Standard Institute in 2000 proposes an additional fracture requirement to the main steel components of the low temperatures storage tank where a partial height hydrostatic test is allowed instead of the full height hydrostatic test required in BS 7777. In the PD7777 a high level (75J) of fracture toughness is required for the austenitic weld metal in 9%Ni steel plate to prevent the re-initiation of ductile fracture from the arrested brittle crack in the weld. This is to report a study that the J-Cv correlation of austenitic weld metal is determined by the experimental data obtained from the actual weld joints in 9%Ni steel plate in order to assess a rational toughness requirement to the austenitic weld metal employed in the 9% Ni made LNG storage tanks. From this study it is concluded that fracture toughness of 75J is too conservative and 50J is adequate. Further some FEM analyses were performed to verify the validity of the weld surrounded by the large amount of heterogeneous base metal in the yield strength distribution.

The Texture Effect on the Dynamic Fracture Properties of Magnesium Alloy AZ31B

2016 ◽  
Vol 715 ◽  
pp. 74-79
Author(s):  
Xia Yu ◽  
Yu Long Li ◽  
Tao Li
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Fracture Surface ◽  
Dynamic Fracture ◽  
Texture Evolution ◽  
Crack Tip ◽  
Image Correlation ◽  
Coarse Grain ◽  
Alloy Plate ◽  
Fine Grain

In this work, Mode I dynamic fracture experiments are conducted on pre-cracked three point bending specimens by using modified split-Hopkinson pressure bar. Two sets of specimens with different initial textures are considered here: one set of the specimens are machined from a hot rolled AZ31B Mg alloy plate with a bigger grain size. The others are treated by four pass of equal channel angular pressing (ECAP) after they are cut from the initial material. They are with the finer grain size. Digital image correlation (DIC) technique is used to determine the strain contours around the crack tip and electron back scatter diffraction (EBSD) is employed to analyze the texture evolution after tests. It is found that the dynamic fracture toughness of finer grain specimen is higher than that of coarse grain specimen. The fracture toughness of both sets of specimens is enhanced by increasing the loading rates. Texture analysis shows the formation of tensile twinning in the ligament ahead of the crack tip in the coarse grain specimen but no sign in fine grain specimen. The brittle features e. g. cleavage planes and twinning lamellas are observed on the fracture surface of coarse grain specimen by scanning electron microscope (SEM). However, the relative ductile features such as micro-voids surrounding by tear ridges present on the fracture surface of fine grain specimen.

scholarly journals Unstable Brittle Crack-Arrest Toughness of Newly Developed Steel Plate with Surface Layers having Ultra Fine Grain Microstructure (2)

1995 ◽  
Vol 1995 (178) ◽  
pp. 555-563 ◽  
Author(s):  
Tadashi Ishikawa ◽  
Takehiro Inoue ◽  
Yukito Hagiwara ◽  
Shigeru Ohshita ◽  
Takao Kuroiwa ◽  
...  
Keyword(s):  
Steel Plate ◽  
Crack Arrest ◽  
Brittle Crack ◽  
Surface Layers ◽  
Fine Grain ◽  
Arrest Toughness

Effect of a Thin Cr Layer on the Microstructures and Fracture Behaviours of Copper Films

2011 ◽  
Vol 194-196 ◽  
pp. 2376-2379
Author(s):  
Hao Liang Sun ◽  
Zhong Xiao Song ◽  
Fei Ma ◽  
Ke Wei Xu
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Brittle Fracture ◽  
Copper Films ◽  
Ductile Rupture ◽  
Cu Films ◽  
Fine Grain ◽  
Deformation And Fracture ◽  
Growth Of Voids ◽  
Fracture Processes

An investigation on Cu/Cr/Si composite thin films demonstrated that a thin Cr layer affects the microstructures and mechanical behavior of Cu films significantly. The fracture modes changes from brittle fracture to ductile rupture, as indicated by the dimpled rupture of Cu films. Moreover, the Cr sticking layer can result in carrot-shaped rods and a fine grain size. Further analysis indicates their deformation and fracture processes are closely related to the coupling of dislocation-mediated plasticity as well as the formation and growth of voids which act as sites for nucleation of the dimples.

scholarly journals Microstructures and Mechanical Properties of Hot-Pressed -Matrix Composites Reinforced with SiC and Particles

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Hongming Zhou ◽  
Jian Li ◽  
Danqing Yi
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Bending Strength ◽  
Testing Machine ◽  
Materials Testing ◽  
Matrix Composites ◽  
Dispersion Strengthening ◽  
Hardness Tester ◽  
Fine Grain ◽  
Fine Grain Strengthening

-matrix composites reinforced with and SiC particles were fabricated by means of wet-mixing and heat-pressing process. Scanning electron microscope (SEM), X-ray diffractometry (XRD), polarizing microscopy, Vickers hardness tester, with a universal materials testing machine were used to investigate the morphology, grain size, hardness, fracture toughness, and bending strength of the synthesized composites. Notable effects on the bending strength and fracture toughness of caused by the addition of SiC and particles were found. The composite with 20 vol.% SiC and 20 vol.% Si3N4 particles has the highest strength and toughness, which is about 100% and 340%, respectively, higher than that of pure . The grain size of decreases gradually with the volume content of SiC and particles increasing from 0% to 40%, and -20 vol% SiC-20 vol% Si3N4 composite exhibits the minimum grain size of . The relationship between the grain size of and bending strength is not entirely fit with Hall-Petch equation. The strengthening mechanisms of the composite include fine-grain strengthening and dispersion strengthening. The toughening mechanisms of the composite include fine grain, microcracking, crack deflection, crack microbridging, and crack branching.

Design and Processing of Niobium Microalloyed Cost Effective Line Pipe Steel With Enhanced Strength and Fracture Toughness

2013 ◽  
Author(s):  
S. V. Subramanian ◽  
J. M. Gray
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Brittle Fracture ◽  
Heat Input ◽  
Large Strain ◽  
Cost Effective ◽  
Accelerated Cooling ◽  
Pipe Steels ◽  
High Angle ◽  
Line Pipe

The functional role of niobium in the original HTP X-80 design of high niobium (0.1wt%), low interstitial ( C 0.03 to 0.04, N<0.005wt%) cost-effective base chemistry is (i) to use Zener drag from strain induced precipitation of NbC during thermo-mechanical rolling and solute drag from solute niobium to retard static recrystallization, (ii) to impart adequate rolling reduction below temperature of no recrystallization to promote large strain accumulation in pancaked austenite, and (iii) to promote fine ferrite grain size by strain induced phase transformation under accelerated cooling conditions, thereby obtain high strength and fracture toughness at low temperature through grain size effect. Residual niobium in austenite is used to impart additional strength through transformation hardening, dislocation hardening from accelerated cooling and precipitation strengthening of ferrite through accelerated cooling and interrupted cooling at coiling temperature. Recent research has confirmed the importance of control of density and dispersion of crystallographic high angle boundaries which are superimposed on the morphological microstructure in order to prevent the initiation of brittle fracture. Extensive research has been carried out in HTP base chemistry to determine the processing options to control the density and dispersion of high angle boundaries to produce higher grade (>X-80) line pipe steels with enhanced fracture toughness. Whereas the resistance to ductile fracture is measured by Charpy toughness, the resistance to brittle fracture is inferred from ductile to brittle transition temperature and percentage shear in DWTT. The research has underscored the importance of austenite grain refinement in upstream processing of HTP before pancaking in finish rolling to control density and dispersion of high angle boundaries in order to prevent brittle fracture initiation. Experimental results are presented which demonstrate that HTP base chemistry is a cost effective design to produce higher grade line pipe steels, not only to achieve high resistance to ductile and brittle fracture in the base plate, but also in HAZ regions associated with relatively high heat input welding in weld fabrication of pipes from plates, and Girth field welding of pipes involving low heat input multi-pass welding.

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